The present invention relates to a method of manufacturing a thin film, a substrate having a thin film, an electron emission material and a method of manufacturing the same, and an electron emission device.
In recent years, application of carbon nanofibers to electromagnetic devices has been studied.
For example, a method of manufacturing a thin film by causing the carbon nanofibers to be directly grown on a substrate has been proposed (e.g. JP-A-11-349307).
However, the size and the shape of the thin film are limited when using the method of causing the carbon nanofibers to be directly grown on a substrate. Moreover, the resulting substrate is expensive due to low manufacturing efficiency.
A method of manufacturing a thin film by spraying a dispersion liquid containing the carbon nanofibers has also been proposed (e.g. JP-A-2003-121892).
However, since the carbon nanofibers are generally produced in the form of an aggregated powder or a bundle, the carbon nanofibers are not uniformly dispersed in the dispersion liquid. Therefore, it is difficult to improve the dispersibility of the carbon nanofibers in the resulting thin film.
In recent years, an electron emission device in which electrons are emitted upon application of an electric field has been proposed for a display (field emission display: FED) such as a thin television or a flat lighting device in order to deal with a demand for energy saving. The electron emission device is required to allow electron emission at a low electric field and have a high current density and long life. The carbon nanofibers proposed as an electron emission material for the electron emission device can achieve a high current density at a low electric field. However, it was found that the carbon nanofibers break during electron emission and therefore have a short life (e.g. JP-A-2003-77386).